Inhibition of histaminase release from human granulocytes by products of histaminase activity.

Imidazoleacetic acid, a product of the action of histaminase (E.C. 1.4.3.6) on histamine, inhibits specific release of histaminase from human peripheral blood granulocytes with an inhibition constant between 5 X 10(-9)M and 1 X 10(-8)M. Hence, modulation of enzyme release is indirectly mediated by the activity of the enzyme.